An underwater breathing apparatus of the above kind is disclosed in U.S. Pat. No. 2,483,116. The known breathing apparatus includes an inhalation bag, an exhalation bag and a buoyancy bag which are all attached to the torso of a diver by individual belts. An inhalation tube leads from the inhalation bag and an exhalation tube leads from the exhalation bag to a diver mask which is provided with directional valves for controlling the breathing gas flow. The two breathing bags are connected to each other via a carbon dioxide absorber which serves to remove the carbon dioxide from the exhaled gas. An oxygen bottle is disposed in a pocket below the breathing bags and is connected to the inhalation bag via a metering valve. A buoyancy bag is arranged below the two breathing bags and can be filled with oxygen as required in order to adjust the upward force in the water to a desired value.
In the known breathing apparatus, by the placement of the oxygen bottle in a pocket (which is configured as an extension of the breathing bags) and the attachment of the buoyancy bag below the breathing bags and the oxygen bottle, the expansion of the buoyancy bag as well as the expansion of the breathing bags are all hindered by the attachment belts. Accordingly, the attachment belts, which are pulled tightly before a diving operation, must again be loosened after diving into the water so that the bags can expand unhindered. This affects the usability of the underwater apparatus. Furthermore, the known breathing apparatus is expensive to manufacture because the breathing bags and the buoyancy bag must be joined as separate components.